Method and apparatus for determining physiological parameters of a subject, and computer-program product thereof

ABSTRACT

A method for determining one or more physiological parameters of a subject. The method includes providing a plurality of images of a vessel of the subject in response to illumination of the vessel to light of different wavelengths; converting each of the plurality of images of the vessel into at least two grayscale images, thereby generating a plurality of first grayscale images of a first wavelength range and a plurality of second grayscale images of a second wavelength range, the first wavelength range and the second wavelength range being different from each other; and determining the one or more physiological parameters of the subject based on at least the plurality of first grayscale images and the plurality of second grayscale images.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage application under 35 U.S.C. § 371of International Application No. PCT/CN2018/119357, filed Dec. 5, 2018,the contents of which are incorporated by reference in the entirety.

TECHNICAL FIELD

The present invention relates to medical device technology, moreparticularly, to a method and an apparatus for determining one or morephysiological parameters of a subject, and a computer-program productthereof.

BACKGROUND

Optical imaging is an emerging technology with potential for improvingdisease prevention, diagnosis, and treatment in the medical office, atthe bedside, or in the operating room. Optical imaging technologies cannoninvasively differentiate among soft tissues, and between native softtissues and tissue labeled with either endogenous or exogenous contrastmedia, using their different photon absorption or scattering profiles atdifferent wavelengths. Such photon absorption and scattering differencesoffers potential for providing specific tissue contrasts, and enablesstudying functional and molecular level activities that are the basisfor health and disease.

SUMMARY

In one aspect, the present invention provides a method for determiningone or more physiological parameters of a subject, comprising providinga plurality of images of a vessel of the subject in response toillumination of the vessel to light of different wavelengths; convertingeach of the plurality of images of the vessel into at least twograyscale images, thereby generating a plurality of first grayscaleimages of a first wavelength range and a plurality of second grayscaleimages of a second wavelength range, the first wavelength range and thesecond wavelength range being different from each other; and determiningthe one or more physiological parameters of the subject based on atleast the plurality of first grayscale images and the plurality ofsecond grayscale images.

Optionally, converting each of the plurality of images of the vesselinto at least two grayscale images comprises determining a first valueof a first color component, a second value of a second color component,and a third value of a third color component for each pixel of aplurality of pixels of each of the plurality of images; determining afirst light intensity in the first wavelength range and a second lightintensity in the second wavelength range for each pixel of the pluralityof pixels, based on the first value, the second value, and the thirdvalue; and generating the plurality of first grayscale images of thefirst wavelength range based on the first light intensity in each pixelof the plurality of pixels and the plurality of second grayscale imagesof the second wavelength range based on the second light intensity ineach pixel of the plurality of pixels.

Optionally, determining the first light intensity in the firstwavelength range and the second light intensity in the second wavelengthrange is performed based on Equation (1):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}}} = e^{(\frac{V_{R^{mn}}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}}} = e^{(\frac{V_{G^{mn}}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}}} = e^{(\frac{V_{B^{mn}}}{K_{B}})}}\end{matrix} \right.;} & (1)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (m, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), K_(R) is a constant coefficientfor the first color component of the pixel (m, n), K_(G) is a constantcoefficient for the second color component of the pixel (m, n), andK_(B) is a constant coefficient for the third color component of thepixel (m, n).

Optionally, converting each of the plurality of images of the vesselinto at least two grayscale images comprises converting each of theplurality of images of the vessel into three grayscale images, therebygenerating the plurality of first grayscale images of the firstwavelength range, the plurality of second grayscale images of the secondwavelength range, and a plurality of third grayscale images of a thirdwavelength range, the first wavelength range, the second wavelengthrange, and the third wavelength range being different from each other;and wherein determining the one or more physiological parameters of thesubject based on at least the plurality of first grayscale images andthe plurality of second grayscale images comprises determining at leasttwo physiological parameters of the subject based on the plurality offirst grayscale images, the plurality of second grayscale images, andthe plurality of third grayscale images.

Optionally, converting each of the plurality of images of the vesselinto three grayscale images comprises determining a first value of afirst color component, a second value of a second color component, and athird value of a third color component for each pixel of a plurality ofpixels of each of the plurality of images; determining a first lightintensity in the first wavelength range, a second light intensity in thesecond wavelength range, and a third light intensity in the thirdwavelength range for each pixel of the plurality of pixels, based on thefirst value, the second value, and the third value; and generating theplurality of first grayscale images of the first wavelength range basedon the first light intensity in each pixel of the plurality of pixels,the plurality of second grayscale images of the second wavelength rangebased on the second light intensity in each pixel of the plurality ofpixels, and the plurality of third grayscale images of the thirdwavelength range based on the third light intensity in each pixel of theplurality of pixels.

Optionally, determining the first light intensity in the firstwavelength range, the second light intensity in the second wavelengthrange, and the third light intensity in the third wavelength range isperformed based on Equation (2):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}} + {Q_{3R}I_{3}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}} + {Q_{3G}I_{3}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}} + {Q_{3B}I_{3}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (2)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (m, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, Q_(3R) stands for aseventh reference quantum efficiency of the first color component of thepixel (m, n) within the third wavelength range, Q_(3G) stands for aneighth reference quantum efficiency of the second color component of thepixel (m, n) within the third wavelength range, Q_(3B) stands for aninth reference quantum efficiency of the third color component of thepixel (m, n) within the third wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), I₃ ^(mn) stands for the thirdlight intensity in the third wavelength range for the pixel (m, n),K_(R) is a constant coefficient for the first color component of thepixel (m, n), K_(G) is a constant coefficient for the second colorcomponent of the pixel (m, n), and K_(B) is a constant coefficient forthe third color component of the pixel (m, n).

Optionally, the method further comprises illuminating the vessel of thesubject with a compound light having a first light of the firstwavelength range, a second light of the second wavelength range, a thirdlight of the third wavelength range; and detecting light reflected by ortransmitted through a body part of the subject using an image sensor,thereby generating the plurality of images of the vessel of the subject.

Optionally, the method further comprises at least one of (1)illuminating the vessel of the subject with a first reference light ofthe first wavelength range and determining a first reference quantumefficiency of the first color component of a pixel within the firstwavelength range, a second reference quantum efficiency of the secondcolor component of the pixel within the first wavelength range, and athird reference quantum efficiency of the third color component of thepixel within the first wavelength range; (2) illuminating the vessel ofthe subject with a second reference light of the second wavelength rangeand determining a fourth reference quantum efficiency of the first colorcomponent of the pixel within the second wavelength range, a fifthreference quantum efficiency of the second color component of the pixelwithin the second wavelength range, and a sixth reference quantumefficiency of the third color component of the pixel within the secondwavelength range; or (3) illuminating the vessel of the subject with athird reference light of a third wavelength range and determining aseventh reference quantum efficiency of the first color component of thepixel within the third wavelength range, an eighth reference quantumefficiency of the second color component of the pixel within the thirdwavelength range, and a ninth reference quantum efficiency of the thirdcolor component of the pixel within the third wavelength range.

Optionally, the first wavelength range and the second wavelength rangeare in a wavelength range of near infrared light and visible light.

Optionally, the first wavelength range is between approximately 760 nmand approximately 850 nm; the second wavelength range is betweenapproximately 850 nm and approximately 960 nm; and the third wavelengthrange is between approximately 530 nm and approximately 660 nm.

Optionally, the one or more physiological parameters of the subjectcomprise a vein pattern, a pulse wave signal, and a blood oxygen levelof the subject.

In another aspect, the present invention provides an apparatus formeasuring one or more physiological parameters of a subject using aplurality of images of a vessel of the subject provided in response toillumination of the vessel to light of different wavelengths, comprisinga memory; and one or more processors; wherein the memory and the one ormore processors are connected with each other; and the memory storescomputer-executable instructions for controlling the one or moreprocessors to convert each of the plurality of images of the vessel intoat least two grayscale images, thereby generating a plurality of firstgrayscale images of a first wavelength range and a plurality of secondgrayscale images of a second wavelength range, the first wavelengthrange and the second wavelength range being different from each other;and determine the one or more physiological parameters of the subjectbased on at least the plurality of first grayscale images and theplurality of second grayscale images.

Optionally, the apparatus further comprises a light source configured toilluminate a vessel of the subject with a compound light having at leasta first light of the first wavelength range and a second light of thesecond wavelength range; and an image sensor configured to detecting thecompound light reflected by or transmitted through a body part of thesubject, thereby generating the plurality of images of the vessel of thesubject.

Optionally, the image sensor is a single image sensor capable ofdetecting the compound light having the first light of the firstwavelength range and the second light of the second wavelength range.

Optionally, the light source is a single light source capable ofsimultaneously emitting the first light of the first wavelength rangeand the second light of the second wavelength range.

Optionally, the memory further stores computer-executable instructionsfor controlling the one or more processors to determine a first value ofa first color component, a second value of a second color component, anda third value of a third color component for each pixel of a pluralityof pixels of each of the plurality of images; determine a first lightintensity in the first wavelength range and a second light intensity inthe second wavelength range for each pixel of the plurality of pixels,based on the first value, the second value, and the third value; andgenerate the plurality of first grayscale images of the first wavelengthrange based on the first light intensity in each pixel of the pluralityof pixels and the plurality of second grayscale images of the secondwavelength range based on the second light intensity in each pixel ofthe plurality of pixels.

Optionally, the memory further stores computer-executable instructionsfor controlling the one or more processors to convert each of theplurality of images of the vessel into three grayscale images, therebygenerating the plurality of first grayscale images of the firstwavelength range, the plurality of second grayscale images of the secondwavelength range, and a plurality of third grayscale images of a thirdwavelength range, the first wavelength range, the second wavelengthrange, and the third wavelength range being different from each other;and determining at least two physiological parameters of the subjectbased on the plurality of first grayscale images, the plurality ofsecond grayscale images, and the plurality of third grayscale images.

Optionally, the memory further stores computer-executable instructionsfor controlling the one or more processors to determine a first value ofa first color component, a second value of a second color component, anda third value of a third color component for each pixel of a pluralityof pixels of each of the plurality of images; determine a first lightintensity in the first wavelength range, a second light intensity in thesecond wavelength range, and a third light intensity in the thirdwavelength range for each pixel of the plurality of pixels, based on thefirst value, the second value, and the third value; and generate theplurality of first grayscale images of the first wavelength range basedon the first light intensity in each pixel of the plurality of pixels,the plurality of second grayscale images of the second wavelength rangebased on the second light intensity in each pixel of the plurality ofpixels, and the plurality of third grayscale images of third wavelengthrange based on the third light intensity in each pixel of the pluralityof pixels.

Optionally, the one or more physiological parameters of the subjectcomprise a vein pattern, a pulse wave signal, and a blood oxygen levelof the subject.

In another aspect, the present invention provides a computer-programproduct comprising a non-transitory tangible computer-readable mediumhaving computer-readable instructions thereon, the computer-readableinstructions being executable by a processor to cause the processor toperform converting each of a plurality of images of a vessel of asubject provided in response to illumination of the vessel to light ofdifferent wavelengths into at least two grayscale images, therebygenerating a plurality of first grayscale images of a first wavelengthrange and a plurality of second grayscale images of a second wavelengthrange, the first wavelength range and the second wavelength range beingdifferent from each other; and determining one or more physiologicalparameters of the subject based on at least the plurality of firstgrayscale images and the plurality of second grayscale images.

BRIEF DESCRIPTION OF THE FIGURES

The following drawings are merely examples for illustrative purposesaccording to various disclosed embodiments and are not intended to limitthe scope of the present invention.

FIG. 1 is a flow chart illustrating a method for determining one or morephysiological parameters of a subject in some embodiments according tothe present disclosure.

FIG. 2 is a flow chart illustrating a method for determining one or morephysiological parameters of a subject in some embodiments according tothe present disclosure.

FIG. 3 is a schematic diagram illustrating an RGB channel separation ofan image in some embodiments according to the present disclosure.

FIG. 4 depicts a curve of quantum efficiency over a wavelength rangebetween 350 nm and 1050 nm of an image recorded for a first colorcomponent of a pixel (the densely dotted line), a second color componentof the pixel (the sparsely dotted line), and a third color component ofthe pixel (the solid line) in some embodiments according to the presentdisclosure.

FIG. 5 is a schematic diagram illustrating an apparatus for measuringone or more physiological parameters of a subject in some embodimentsaccording to the present disclosure.

FIG. 6 is a schematic diagram illustrating an apparatus for measuringone or more physiological parameters of a subject in some embodimentsaccording to the present disclosure.

DETAILED DESCRIPTION

The disclosure will now be described more specifically with reference tothe following embodiments. It is to be noted that the followingdescriptions of some embodiments are presented herein for purpose ofillustration and description only. It is not intended to be exhaustiveor to be limited to the precise form disclosed.

Various apparatuses have been developed to detect physiologicalparameters of a subject. However, to measure multiple physiologicalparameters of the subject, it is required to take the measurementsseveral times to obtain distinct biometric signals for each of themeasurements, resulting in poor user experience. Even if multipleapparatuses are integrated into a device, these apparatuses stillrequire separate set-ups, such as separate light sources and separatesensors. Thus, the manufacturing costs remains high, and it is difficultto miniaturize the device.

Accordingly, the present disclosure provides, inter alia, a method fordetermining one or more physiological parameters of a subject, anapparatus for determining one or more physiological parameters of asubject, and a computer-program product thereof that substantiallyobviate one or more of the problems due to limitations and disadvantagesof the related art. In one aspect, the present disclosure provides amethod for determining one or more physiological parameters of asubject. FIG. 1 is a flow chart illustrating a method for determiningone or more physiological parameters of a subject in some embodimentsaccording to the present disclosure. Referring to FIG. 1, the method insome embodiments includes providing a plurality of images of a vessel ofthe subject in response to illumination of the vessel to light ofdifferent wavelengths; converting each of the plurality of images of thevessel into at least two grayscale images, thereby generating aplurality of first grayscale images of a first wavelength range and aplurality of second grayscale images of a second wavelength range, thefirst wavelength range and the second wavelength range being differentfrom each other; and determining the one or more physiologicalparameters of the subject based on at least the plurality of firstgrayscale images and the plurality of second grayscale images. Asreferred to herein, the term “physiological parameter” refers ahealth-related parameter of the subject. A physiological parameter maybe directly and/or indirectly measured, detected and/or derived from ameasurement of a device, for example, via a sensor. In some embodiments,the physiological parameter may include such parameters as, but notlimited to blood related parameters, such as, vein pattern, pulse waveparameters (e.g., pulse wave velocity, pulse rate, pulse transit time),blood chemical level (e.g., blood oxygen level, blood cholesterol level,blood glucose level), blood pressure, heart rate, or combinationsthereof. As used herein, the term “vessel” comprises any conduit andincludes an artery or vein. As used herein, the term “subject” refers toa mammal, including both human and other mammals.

Optionally, the first wavelength range and the second wavelength rangeare non-overlapping ranges. Optionally, the first wavelength range andthe second wavelength range are partially overlapping ranges.

FIG. 2 is a flow chart illustrating a method for determining one or morephysiological parameters of a subject in some embodiments according tothe present disclosure. Referring to FIG. 2, the step of converting eachof the plurality of images of the vessel into at least two grayscaleimages in some embodiments includes determining a first value of a firstcolor component, a second value of a second color component, and a thirdvalue of a third color component for each pixel of a plurality of pixelsof each of the plurality of images; determining a first light intensityin the first wavelength range and a second light intensity in the secondwavelength range for each pixel of the plurality of pixels, based on thefirst value, the second value, and the third value; and generating theplurality of first grayscale images of the first wavelength range basedon the first light intensity in each pixel of the plurality of pixelsand the plurality of second grayscale images of the second wavelengthrange based on the second light intensity in each pixel of the pluralityof pixels.

For example, the first color component, the second color component, andthe third color component of the pixel may be a red component, a greencomponent, and a blue component of the image in the pixel. FIG. 3 is aschematic diagram illustrating an RGB channel separation of an image insome embodiments according to the present disclosure. The image in eachpixel of the plurality of pixels is separated into three color channels,e.g., a red color channel (R), a green color channel (G), and a bluecolor channel (B). The first value for the red component, the secondvalue for the green component, and the third value for the bluecomponent, are determined. In one example, the first value, the secondvalue, and the third value can be represented by grayscale values of thered color channel, the green color channel, and the blue color channel.Based on the first value, the second value, and the third value, thefirst light intensity in the first wavelength range and the second lightintensity in the second wavelength range, for each pixel of theplurality of pixels, are determined. Optionally, the first wavelengthrange and the second wavelength range are in a wavelength range of nearinfrared light and visible light. In one example, the first wavelengthrange is a wavelength range of a near infrared light, and the secondwavelength range is a wavelength range of a visible light. In anotherexample, the first wavelength range is a wavelength range of a nearinfrared light, and the second wavelength range is a wavelength range ofa near infrared light. Optionally, the first wavelength range is betweenapproximately 760 nm and approximately 850 nm; and the second wavelengthrange is between approximately 850 nm and approximately 960 nm.Optionally, the first wavelength range is between approximately 760 nmand approximately 850 nm; and the second wavelength range is betweenapproximately 530 nm and approximately 660 nm. Optionally, the firstwavelength range is between approximately 850 nm and approximately 960nm; and the second wavelength range is between approximately 530 nm andapproximately 660 nm. Once the first light intensity in the firstwavelength range for each pixel is determined, the plurality of firstgrayscale images of the first wavelength range can be generated. Oncethe second light intensity in the second wavelength range for each pixelis determined, the plurality of second grayscale images can begenerated.

FIG. 4 depicts a curve of quantum efficiency over a wavelength rangebetween 350 nm and 1050 nm of an image recorded for a first colorcomponent of a pixel (the densely dotted line), a second color componentof the pixel (the sparsely dotted line), and a third color component ofthe pixel (the solid line) in some embodiments according to the presentdisclosure. Referring to FIG. 4, variation of quantum efficiency of afirst color component of the pixel over a wavelength range from 350 nmto 1050 nm is shown as the densely dotted line; variation of quantumefficiency of a second color component of the pixel over a wavelengthrange from 350 nm to 1050 nm is shown as the sparsely dotted line; andvariation of quantum efficiency of a third color component of the pixelover a wavelength range from 350 nm to 1050 nm is shown as the solidline.

With reference to each reference light (e.g., each of the firstreference light, the second reference light, and the third referencelight), a quantum efficiency of a color component of the pixel at aparticular wavelength is a fixed value. For example, and referring toFIG. 4, Quantum efficiencies of the first color component of the pixelrespectively at the first wavelength, the second wavelength, and thethird wavelength are fixed values. Similarly, quantum efficiencies ofthe second color component of the pixel respectively at the firstwavelength, the second wavelength, and the third wavelength are fixedvalues; and quantum efficiencies of the third color component of thepixel respectively at the first wavelength, the second wavelength, andthe third wavelength are fixed values. These quantum efficiencies can bepredetermined, e.g., using each individual reference light as acalibration.

In some embodiments, the first light intensity in the first wavelengthrange and the second light intensity in the second wavelength range canbe determined based on Equation (1):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (1)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (in, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), K_(R) is a constant coefficientfor the first color component of the pixel (m, n), K_(G) is a constantcoefficient for the second color component of the pixel (m, n), andK_(B) is a constant coefficient for the third color component of thepixel (m, n).

As discussed above, Q_(1R), Q_(1G), Q_(1B), Q_(2R), Q_(2G), and Q_(2B)are fixed values, and may be obtained by a calibration test. The threevalues V_(R) ^(mn), V_(G) ^(mn), and V_(B) ^(mn) may be measured byseparating the image in each pixel of the plurality of pixels into threedifferent color channels (e.g., a red color channel, a green colorchannel, and a blue color channel). Optionally, V_(R) ^(mn), V_(G)^(mn), and V_(B) ^(mn) may be represented by grayscale values. Based onEquation (1), the first light intensity in the first wavelength rangefor the pixel (m, n), I₁ ^(mn), and the second light intensity in thesecond wavelength range for the pixel (m, n), I₂ ^(mn), can bedetermined.

In some embodiments, an image sensor is used to detect a compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject. Indetermining the first light intensity in the first wavelength range andthe second light intensity in the second wavelength range, parameters ofthe image sensor are maintained substantially unchanged. For example,parameters affecting the RGB values of an output image of the imagesensor, including aperture, exposure time, focal length, and gain, aremaintained substantially unchanged in the process of determining thefirst light intensity and the second light intensity. Frame rate can beadjusted as long as the frame interval is greater than the exposuretime.

Constant coefficient K_(R), K_(G), and K_(B) are independent of thewavelength. These constant coefficients are determined by severalwavelength-independent factors such as pixel area, exposure time,amplification gain, and tuning algorithm. Optionally, the constantcoefficients may be determined by calibration. For example, the constantcoefficient K_(R) can be determined based on Equation (2):

$\begin{matrix}{{K_{R} = \frac{V_{R\; 0}}{\ln\left( {Q_{0R}I_{0}} \right)}};} & (2)\end{matrix}$

wherein Q_(0R) stands for a reference quantum efficiency of the firstcolor component of the pixel at a reference wavelength, I₀ stands for alight intensity at the reference wavelength for the pixel, V_(R0) standsfor a reference value (e.g., a grayscale value) of the first colorcomponent for the pixel. The constant coefficients K_(G) and K_(B) canbe determined in a similar fashion.

Equation (1) can be expressed as follows:

$\begin{matrix}{{{\overset{\sim}{Q}{\overset{\sim}{I}}^{mn}} = e^{{(\begin{matrix}\frac{V_{R}^{mn}}{K_{R}} \\\frac{V_{G}^{mn}}{K_{G}} \\\frac{V_{B}^{mn}}{K_{B}}\end{matrix})}^{mn}}},{\overset{\sim}{Q} = \begin{pmatrix}Q_{1R} & Q_{2R} \\Q_{1G} & Q_{2G} \\Q_{1B} & Q_{2B}\end{pmatrix}},{\overset{\sim}{I} = {\begin{pmatrix}I_{1} \\I_{2}\end{pmatrix}.}}} & (3)\end{matrix}$

An optimal solution for Ĩ^(mn) may be obtained such that a residualerror E(Ĩ^(mn)) is minimized, wherein the residual error can beexpressed as:

$\begin{matrix}{{E\left( {\overset{\sim}{I}}^{mn} \right)} = {{{{\overset{\sim}{Q}{\overset{\sim}{I}}^{mn}} = e^{{(\begin{matrix}\frac{V_{R}^{mn}}{K_{R}} \\\frac{V_{G}^{mn}}{K_{G}} \\\frac{V_{B}^{mn}}{K_{B}}\end{matrix})}^{mn}}}}.}} & (4)\end{matrix}$

Upon determination of the first light intensity in the first wavelengthrange and the second light intensity in the second wavelength range foreach pixel of the plurality of pixels, the plurality of first grayscaleimages of the first wavelength range and the plurality of secondgrayscale images of the second wavelength range can be generated. Theplurality of first grayscale images and the plurality of secondgrayscale images can then be used for determining one or morephysiological parameters of the subject. In one example, the pluralityof first grayscale images and the plurality of second grayscale imagesare used to determine a blood oxygen level of the subject. In anotherexample, the plurality of first grayscale images are used to determine avein pattern of the subject, and the plurality of second grayscaleimages are used to determine a pulse wave signal of the subject.

In some embodiments, the method includes converting each of theplurality of images of the vessel into three grayscale images, therebygenerating the plurality of first grayscale images of the firstwavelength range, the plurality of second grayscale images of the secondwavelength range, and a plurality of third grayscale images of a thirdwavelength range. The first wavelength range, the second wavelengthrange, and the third wavelength range are different from each other.Optionally, any two ranges of the first wavelength range, the secondwavelength range, and the third wavelength range are non-overlappingwith respect to each other. Optionally, two ranges of the firstwavelength range, the second wavelength range, and the third wavelengthrange are partially overlapping with respect to each other. Optionally,the first wavelength range, the second wavelength range, and the thirdwavelength range are partially overlapping with respect to each other.

The one or more physiological parameters of the subject are determinedbased on the plurality of first grayscale images, the plurality ofsecond grayscale images, and the plurality of third grayscale images.

In some embodiments, the step of converting each of the plurality ofimages of the vessel into three grayscale images includes determining afirst value of a first color component, a second value of a second colorcomponent, and a third value of a third color component for each pixelof a plurality of pixels of each of the plurality of images; determininga first light intensity in the first wavelength range, a second lightintensity in the second wavelength range, and a third light intensity inthe third wavelength range for each pixel of the plurality of pixels,based on the first value, the second value, and the third value; andgenerating the plurality of first grayscale images of the firstwavelength range based on the first light intensity in each pixel of theplurality of pixels, the plurality of second grayscale images of thesecond wavelength range based on the second light intensity in eachpixel of the plurality of pixels, and the plurality of third grayscaleimages of the third wavelength range based on the third light intensityin each pixel of the plurality of pixels.

For example, the first color component, the second color component, andthe third color component of the pixel may be a red component, a greencomponent, and a blue component of the image in the pixel. The image ineach pixel of the plurality of pixels is separated into three colorchannels, e.g., a red color channel, a green color channel, and a bluecolor channel. The first value for the red component, the second valuefor the green component, and the third value for the blue component, aredetermined. Based on the first value, the second value, and the thirdvalue, the first light intensity in the first wavelength range, thesecond light intensity in the second wavelength range, and the thirdlight intensity in the third wavelength range, for each pixel of theplurality of pixels, are then determined. Optionally, the firstwavelength range and the second wavelength range are in a wavelengthrange of near infrared light, and the third wavelength range is in awavelength range of visible light. Optionally, the first wavelengthrange is between approximately 760 nm and approximately 850 nm, thesecond wavelength range is between approximately 850 nm andapproximately 960 nm, and the third wavelength range is betweenapproximately 530 nm and approximately 660 nm. Once the first lightintensity in the first wavelength range for each pixel is determined,the plurality of first grayscale images of the first wavelength rangecan be generated. Once the second light intensity in the secondwavelength range for each pixel is determined, the plurality of secondgrayscale images can be generated. Once the third light intensity in thethird wavelength range for each pixel is determined, the plurality ofthird grayscale images can be generated.

In some embodiments, the first light intensity in the first wavelengthrange, the second light intensity in the second wavelength range, andthe third light intensity in the third wavelength range can bedetermined based on Equation (5):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}} + {Q_{3R}I_{3}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}} + {Q_{3G}I_{3}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}} + {Q_{3B}I_{3}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (5)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (m, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, Q_(3R) stands for aseventh reference quantum efficiency of the first color component of thepixel (m, n) within the third wavelength range, Q_(3G) stands for aneighth reference quantum efficiency of the second color component of thepixel (m, n) within the third wavelength range, Q_(3B) stands for aninth reference quantum efficiency of the third color component of thepixel (m, n) within the third wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), I₃ ^(mn) stands for the thirdlight intensity in the third wavelength range for the pixel (m, n),K_(R) is a constant coefficient for the first color component of thepixel (m, n), K_(G) is a constant coefficient for the second colorcomponent of the pixel (m, n), and K_(B) is a constant coefficient forthe third color component of the pixel (m, n).

As discussed above, Q_(1R), Q_(1G), Q_(1B), Q_(2R), Q_(2G), Q_(2B),Q_(3R), Q_(3G), and Q_(3B) are fixed values, and may be obtained by acalibration test. The three values V_(R) ^(mn), V_(G) ^(mn), and V_(B)^(mn) may be measured by separating the image in each pixel of theplurality of pixels into three different color channels (e.g., a redcolor channel, a green color channel, and a blue color channel).Optionally, V_(R) ^(mn), V_(G) ^(mn), and V_(B) ^(mn) may be representedby grayscale values. Based on Equation (5), the first light intensity inthe first wavelength range for the pixel (m, n), I₁ ^(mn), the secondlight intensity in the second wavelength range for the pixel (m, n), I₂^(mn), and the third light intensity in the third wavelength range forthe pixel (m, n), I₃ ^(mn), can be determined.

In some embodiments, an image sensor is used to detect a compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject. Indetermining the first light intensity in the first wavelength range, thesecond light intensity in the second wavelength range and the thirdlight intensity in the third wavelength range, parameters of the imagesensor are maintained substantially unchanged. For example, parametersaffecting the RGB values of an output image of the image sensor,including aperture, exposure time, focal length, and gain, aremaintained substantially unchanged in the process of determining thefirst light intensity, the second light intensity and the third lightintensity. Frame rate can be adjusted as long as the frame interval isgreater than the exposure time.

Further, Equation (5) can be expressed as follows:

$\begin{matrix}{{{\overset{\sim}{Q}{\overset{\sim}{I}}^{mn}} = e^{{(\begin{matrix}\frac{V_{R}^{mn}}{K_{R}} \\\frac{V_{G}^{mn}}{K_{G}} \\\frac{V_{B}^{mn}}{K_{B}}\end{matrix})}^{mn}}},{\overset{\sim}{Q} = \begin{pmatrix}Q_{1R} & Q_{2R} & Q_{3R} \\Q_{1G} & Q_{2G} & Q_{3G} \\Q_{1B} & Q_{2B} & Q_{3B}\end{pmatrix}},{\overset{\sim}{I} = {\begin{pmatrix}I_{1} \\I_{2} \\I_{3}\end{pmatrix}.}}} & (6) \\{{Thus},{{\overset{\sim}{I}}^{mn} = {{\overset{\sim}{Q}}^{- 1}{{e\begin{pmatrix}\frac{V_{R}^{mn}}{K_{R}} \\\frac{V_{G}^{mn}}{K_{G}} \\\frac{V_{B}^{mn}}{K_{B}}\end{pmatrix}}^{mn}.}}}} & (7)\end{matrix}$

The first wavelength range, the second wavelength range, and the thirdwavelength range can be selected to have appropriate values, and anappropriate image sensor can be selected, so that |Q|≠0.

Upon determination of the first light intensity in the first wavelengthrange, the second light intensity in the second wavelength range, andthe third light intensity in the third wavelength range, for each pixelof the plurality of pixels, the plurality of first grayscale images ofthe first wavelength range, the plurality of second grayscale images ofthe second wavelength range, and the plurality of third grayscale imagesof the third wavelength range, can be generated. The plurality of firstgrayscale images, the plurality of second grayscale images, and theplurality of third grayscale images can then be used for determining oneor more physiological parameters of the subject. In one example, theplurality of first grayscale images are used to determine a vein patternof the subject, the plurality of second grayscale images are used todetermine a pulse wave signal of the subject, and the plurality ofsecond grayscale images and the plurality of third grayscale images areused to determine a blood oxygen level of the subject.

In some embodiments, the method further includes providing the pluralityof images of the vessel of the subject in response to illumination ofthe vessel to light of different wavelengths. Optionally, the methodincludes illuminating the vessel of the subject with a compound lighthaving a first light of the first wavelength range, a second light ofthe second wavelength range, a third light of the third wavelengthrange; and detecting light reflected by or transmitted through a bodypart of the subject using an image sensor, thereby generating theplurality of images of the vessel of the subject. The light source usedfor illuminating the vessel of the subject in some embodiments is asingle light source. Optionally, the light source used for illuminatingthe vessel of the subject includes a plurality of light emittingelements, e.g., a first light emitting element for emitting the firstlight of the first wavelength range, a second light emitting element foremitting the second light of the second wavelength range, and a thirdlight emitting element for emitting the third light of the thirdwavelength range.

In some embodiments, the method further includes a calibration step todetermine one or more of Q_(1R), Q_(1G), Q_(1B), Q_(2R), Q_(2G), Q_(2B),Q_(3R), Q_(3G), and Q_(3B). Optionally, the method includes illuminatingthe vessel of the subject with a first reference light of the firstwavelength range and determining a first reference quantum efficiency ofthe first color component of a pixel within the first wavelength range,a second reference quantum efficiency of the second color component ofthe pixel within the first wavelength range, and a third referencequantum efficiency of the third color component of the pixel within thefirst wavelength range. In one example, the first reference quantumefficiency is Q_(1R), the second reference quantum efficiency is Q_(1G),and the third reference quantum efficiency is Q_(1B). Optionally, themethod includes illuminating the vessel of the subject with a secondreference light of the second wavelength range and determining a fourthreference quantum efficiency of the first color component of the pixelwithin the second wavelength range, a fifth reference quantum efficiencyof the second color component of the pixel within the second wavelengthrange, and a sixth reference quantum efficiency of the third colorcomponent of the pixel within the second wavelength range. In anotherexample, the fourth reference quantum efficiency is Q_(2R), the fifthreference quantum efficiency is Q_(2G), and the sixth reference quantumefficiency is Q_(2B). Optionally, the method includes illuminating thevessel of the subject with a third reference light of the thirdwavelength range and determining a seventh reference quantum efficiencyof the first color component of the pixel within the third wavelengthrange, an eighth reference quantum efficiency of the second colorcomponent of the pixel within the third wavelength range, and a ninthreference quantum efficiency of the third color component of the pixelwithin the third wavelength range. In another example, the seventhreference quantum efficiency is Q_(3R), the eighth reference quantumefficiency is Q_(3G), and the ninth reference quantum efficiency isQ_(3B).

Various appropriate methods may be used for detecting blood oxygenlevels. In one example, a plurality of images of a body part of asubject (e.g., skin) can be captured using an image sensor to record thereflection or transmission of light through an anatomical extremity,such as a human finger. Image characteristics corresponding to theplurality of first grayscale images at a first wavelength range (e.g., afirst wavelength) can be compared with image characteristicscorresponding to the plurality of second grayscale images at a secondwavelength range (e.g., a second wavelength). The second wavelength issubstantially distinct from the first wavelength. Blood oxygen level canbe determined based on comparing the image characteristics.

In one example, oxygen saturation of a subject can be determined usingan image sensor. A user can place his/her finger in proximity to theimage sensor and a video or picture sequence can be captured. Imageanalysis and signal processing techniques can then be used on thecaptured sequence to process and extract oxygen saturation (SpO₂). Theprocessing can be done either in real-time, such as while the picturesequence is being captured, or can be done off-line after the picturesequence has been captured.

In another example, SpO₂ can be determined according to:

$\begin{matrix}{{{SpO}_{2} = \frac{C_{0}}{C_{0} + C_{r}}};} & (8)\end{matrix}$

wherein SpO₂ stands for oxygen saturation, C₀ stands for oxygenatedhemoglobin concentration, and Cr stands for deoxyhemoglobinconcentration. According to Beer-Lambert's law for absorption of lightthrough materials:I _(out) =I _(in)*10^(−(α) ⁰ ^(C) ⁰ ^(+α) ^(r) ^(C) ^(r) ^()l)  (9);

for light with wavelength l and where I_(in) is intensity of lightpassed through an artery of thickness 1, I_(out) is intensity of lightexiting the artery, α₀ is the absorption coefficient of oxygenated bloodat wavelength λ, and α_(r) is the absorption coefficient of deoxygenatedblood at wavelength λ. In order to solve for 2 variables, namelyvariables C₀ and C_(r), a differential technique wherein 2 wavelengthsof light can be used where:I ₁ =I _(in1)*10^(−(α) ⁰¹ ^(C) ⁰ ^(+α) ^(r1) ^(c) ^(r) ^()l)  (10);at wavelength λ1, andI ₂ =I _(in2)*10^(−(α) ⁰² ^(C) ⁰ ^(+α) ^(r2) ^(c) ^(r) ^()l)  (11);at wavelength λ2.

Thus,

$\begin{matrix}{{\frac{C_{0}}{C_{0} + C_{r}} = \frac{{\alpha_{r\; 2}R} - \alpha_{r\; 1}}{\left( {\alpha_{r2} - \alpha_{02}} \right) - \left( {\alpha_{r1} - \alpha_{01}} \right)}};} & (12)\end{matrix}$

wherein

$\begin{matrix}{{R = \frac{\log_{10}\left( \frac{I_{1}}{I_{in1}} \right)}{\log_{10}\left( \frac{I_{2}}{I_{in2}} \right)}}.} & (13)\end{matrix}$

The value of R can be calculated by measuring the voltages at the outputof photodiodes/pixels in the image sensor:

$\begin{matrix}{{R = \frac{{\log_{10}\left( \frac{V_{ac} + V_{dc}}{V_{dc}} \right)}\mspace{14mu}{for}\mspace{14mu}{\lambda 1}}{{\log_{10}\left( \frac{V_{ac} + V_{dc}}{V_{dc}} \right)}\mspace{14mu}{for}\mspace{14mu}{\lambda 2}}}.} & (14)\end{matrix}$

Accordingly, the oxygen saturation can be determined.

Various appropriate methods may be used for detecting pulse wavesignals. In one example, the pulse wave signals are detected byPhotoplethysmography imaging (PPGi). In PPG imaging, backscattered lightfrom a tissue is analyzed. When light irradiates on the tissue, aportion of that light scatters within the tissue, then interacts withthe chromophores in the blood, and eventually is scattered back throughthe tissue surface (e.g., skin). When observed over time, thislight-tissue interaction superimposes a weak AC modulation that isapproximately 1-2% compared to the total amount of light reflected fromthe tissue. The small AC signal of this back-scattered light can beanalyzed to obtain information regarding the position, relative bloodvolume, and relative blood concentration of the arterial circulation.Images generated from this information provide a method to assesspathologies involving changes to tissue blood flow and pulse rateincluding: tissue perfusion; cardiovascular health; wounds such asulcers; peripheral arterial disease, and respiratory health. In oneexample, a near infrared light is used as illumination source to takeadvantage of the increased photon penetration into the tissue at thiswavelength. A common setup includes positioning the light source nearthe target tissue to be imaged. This usually requires high dynamic rangeand low-light sensitive sensors to detect the PPG signal.

Various appropriate methods may be used for recognizing vein patterns.In one example, the vein pattern of a subject may be recognized byirradiating a body part of the subject with a near infrared light. Lightis reflected by or transmits through the body part, after the lightdiffusing through the body part. The deoxidized hemoglobin in the veinvessels absorb the infrared ray, thereby reducing the reflection rate ortransmission rate and causing the veins to appear as a black pattern. Inone example, the vein pattern is verified against a preregisteredpattern to authenticate a subject.

In another aspect, the present disclosure provides an apparatus formeasuring one or more physiological parameters of a subject using aplurality of images of a vessel of the subject provided in response toillumination of the vessel to light of different wavelengths. In someembodiments, the apparatus includes a memory; and one or moreprocessors. The memory and the one or more processors are connected witheach other. In some embodiments, the memory stores computer-executableinstructions for controlling the one or more processors to convert eachof the plurality of images of the vessel into at least two grayscaleimages, thereby generating a plurality of first grayscale images of afirst wavelength range and a plurality of second grayscale images of asecond wavelength range, the first wavelength range and the secondwavelength range being different from each other; and determine the oneor more physiological parameters of the subject based on at least theplurality of first grayscale images and the plurality of secondgrayscale images.

FIG. 5 is a schematic diagram illustrating an apparatus for measuringone or more physiological parameters of a subject in some embodimentsaccording to the present disclosure. Referring to FIG. 5, the apparatusin some embodiments includes a processor 104 and a memory 107 connectedwith each other. The memory 107 stores computer-executable instructionsfor controlling the processor 104 to perform the functions describedabove. FIG. 6 is a schematic diagram illustrating an apparatus formeasuring one or more physiological parameters of a subject in someembodiments according to the present disclosure. Referring to FIG. 6,the apparatus in some embodiments includes a processor 104 and a memory107 connected with each other. The memory 107 stores computer-executableinstructions for controlling the processor 104 to perform the functionsdescribed above.

Various appropriate memories may be used in the present apparatus.Examples of appropriate memories include, but are not limited to,various types of processor-readable media such as random access memory(RAM), read-only memory (ROM), non-volatile random access memory(NVRAM), programmable read-only memory (PROM), erasable programmableread-only memory (EPROM), electrically erasable PROM (EEPROM), flashmemory, magnetic or optical data storage, registers, magnetic disk ortape, optical storage media such as compact disk (CD) or DVD (digitalversatile disk), and other non-transitory media. Optionally, the memoryis a non-transitory memory. Various appropriate processors may be usedin the present apparatus. Examples of appropriate processors include,but are not limited to, a general-purpose processor, a centralprocessing unit (CPU), a microprocessor, a digital signal processor(DSP), a controller, a microcontroller, a state machine, etc.

Referring to FIG. 5, the apparatus in some embodiments further includesa light source 101 configured to emit light of multiple wavelengths, animage sensor 102 below the light source 101, and a body 103 forming achamber having an opening on a lateral side. The image sensor 102 may bea color image sensor. The chamber formed by the body 103 preventsambient light from interfering with the light detection of the imagesensor 102. A body part 106 may be placed into the chamber through theopening on the lateral side of the body 103. The body part 106 may beplaced between the light source 101 and the image sensor 102, so thatthe image sensor 102 may detect light transmitted through the body part106 of the subject. The processor 104 is configured to acquire from theimage sensor 102 a plurality of images of a vessel of the subject inresponse to illumination of the vessel to light of differentwavelengths. The apparatus further includes a power source 105configured to provide power supply for the light source 101, the imagesensor 102, the memory 107, and the processor 104.

Referring to FIG. 6, the apparatus in some embodiments further includesa support 201 configured to support a body part 106 of the subject.Similar to the apparatus as shown in FIG. 5, the apparatus in FIG. 6also includes a light source 101 configured to emit light of multiplewavelengths, an image sensor 102 below the light source 101, and a body103 forming a chamber having an opening on a lateral side. The imagesensor 102 may be a color image sensor. The chamber formed by the body103 prevents ambient light from interfering with the light detection ofthe image sensor 102. A body part 106 may be placed into the chamberthrough the opening on the lateral side of the body 103. In theapparatus as shown in FIG. 6, the light source 101 is configured to emitlight upwards, toward the body part 106 placed on the support 201.Optionally, the body part 106 is placed in close proximity to the lightsource 101. The image sensor 102 placed below the body part 106 isconfigured to detect light reflected by the body part 106 of thesubject. The processor 104 is configured to acquire from the imagesensor 102 a plurality of images of a vessel of the subject in responseto illumination of the vessel to light of different wavelengths. Theapparatus further includes a power source 105 configured to providepower supply for the light source 101, the image sensor 102, the memory107, and the processor 104.

In some embodiments, the light source 101 is configured to illuminate avessel (in the body part 106) of the subject with a compound lighthaving a first light of the first wavelength range and a second light ofthe second wavelength range. Optionally, the first wavelength range andthe second wavelength range are in a wavelength range of near infraredlight and visible light. In one example, the first wavelength range is awavelength range of a near infrared light, and the second wavelengthrange is a wavelength range of a visible light. In another example, thefirst wavelength range is a wavelength range of a near infrared light,and the second wavelength range is a wavelength range of a near infraredlight. Optionally, the first wavelength range is between approximately760 nm and approximately 850 nm; and the second wavelength range isbetween approximately 850 nm and approximately 960 nm. Optionally, thefirst wavelength range is between approximately 760 nm and approximately850 nm; and the second wavelength range is between approximately 530 nmand approximately 660 nm. Optionally, the first wavelength range isbetween approximately 850 nm and approximately 960 nm; and the secondwavelength range is between approximately 530 nm and approximately 660nm.

In some embodiments, the light source 101 is configured to illuminate avessel (in the body part 106) of the subject with a compound lighthaving a first light of the first wavelength range, a second light ofthe second wavelength range, a third light of the third wavelengthrange. Optionally, the first wavelength range and the second wavelengthrange are in a wavelength range of near infrared light, and the thirdwavelength range is in a wavelength range of visible light. Optionally,the first wavelength range is between approximately 760 nm andapproximately 850 nm; the second wavelength range is betweenapproximately 850 nm and approximately 960 nm; and the third wavelengthrange is between approximately 530 nm and approximately 660 nm. Theabsorption peak for deoxyhemoglobin is approximately 760 nm. Theabsorption peak for oxygenated hemoglobin is approximately 910 nm. Thus,grayscale images taken at approximately 760 nm and approximately 660 nmmay be used for detecting blood oxygen level (660 nm as the reference).Grayscale images taken at approximately 760 nm may be used for detectingvein pattern. Grayscale images taken at approximately 910 nm may be usedfor detecting pulse wave signals.

Optionally, the light source 101 is a single light source capable ofsimultaneously emitting the first light of the first wavelength rangeand the second light of the second wavelength range. Optionally, thelight source 101 is a single light source capable of simultaneouslyemitting the first light of the first wavelength range, the second lightof the second wavelength range, the third light of the third wavelengthrange. In one example, the light source 101 includes a white light and aplurality of fluorescent/phosphor layers. The plurality offluorescent/phosphor layers are respectively configured to emit light ofdifferent wavelengths upon irradiation of white light. In anotherexample, the light source 101 includes a white light and a plurality ofcolor filter blocks. The plurality of color filter blocks arerespectively configured to transmit light of different wavelengths uponirradiation of white light. In another example, light source 101includes a plurality of light emitting diodes respectively configured toemit light of different wavelengths.

Optionally, the light source 101 includes a plurality of light emittingelements (e.g., light emitting diodes) respectively configured to emitlight of different wavelengths. Optionally, the light source 101includes at least two light emitting elements, one configured to emitthe first light of the first wavelength range and the other configuredto emit the second light of the second wavelength range. Optionally, thelight source 101 includes three light emitting elements, the firstconfigured to emit the first light of the first wavelength range, thesecond configured to emit the second light of the second wavelengthrange, and the third configured to emit the third light of the thirdwavelength range.

The image sensor 102 is configured to detecting the compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject.Optionally, the image sensor 102 is a single image sensor capable ofdetecting the compound light having at least the first light of thefirst wavelength range and the second light of the second wavelengthrange. Optionally, the image sensor 102 is a single image sensor capableof detecting the compound light having the first light of the firstwavelength range, the second light of the second wavelength range, thethird light of the third wavelength range.

Various appropriate image sensors may be used in the present apparatus.Examples of appropriate image sensors include a charged coupled device(CCD) image sensor and a complementary metal-oxide semiconductor (CMOS)image sensor. Optionally, the image sensor 102 is a color image sensorcapable of detecting different colors, e.g., red color, green color, andblue color. Optionally, the image sensor 102 is capable of detectingsignals in a long wavelength range, e.g., up to 1050 nm. Optionally, theimage sensor 102 has a frame rate of at least 8 fps, e.g., greater than25 fps.

In some embodiments, the memory further stores computer-executableinstructions for controlling the one or more processors to determine afirst value of a first color component, a second value of a second colorcomponent, and a third value of a third color component for each pixelof a plurality of pixels of each of the plurality of images; determine afirst light intensity in the first wavelength range and a second lightintensity in the second wavelength range for each pixel of the pluralityof pixels, based on the first value, the second value, and the thirdvalue; and generate the plurality of first grayscale images of the firstwavelength range based on the first light intensity in each pixel of theplurality of pixels and the plurality of second grayscale images of thesecond wavelength range based on the second light intensity in eachpixel of the plurality of pixels.

In some embodiments, the memory further stores computer-executableinstructions for controlling the one or more processors to determine thefirst light intensity in the first wavelength range and the second lightintensity in the second wavelength range according to Equation (1):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (1)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (m, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), K_(R) is a constant coefficientfor the first color component of the pixel (m, n), K_(G) is a constantcoefficient for the second color component of the pixel (m, n), andK_(B) is a constant coefficient for the third color component of thepixel (m, n).

As discussed above, Q_(1R), Q_(1G), Q_(1B), Q_(2R), Q_(2G), and Q_(2B)are fixed values, and may be obtained by a calibration test. The threevalues V_(R) ^(mn), V_(G) ^(mn), and V_(B) ^(mn) may be measured byseparating the image in each pixel of the plurality of pixels into threedifferent color channels (e.g., a red color channel, a green colorchannel, and a blue color channel). Optionally, V_(R) ^(mn), V_(G)^(mn), and V_(B) ^(mn) may be represented by grayscale values. Based onEquation (1), the first light intensity in the first wavelength rangefor the pixel (m, n), I₁ ^(mn), and the second light intensity in thesecond wavelength range for the pixel (m, n), I₂ ^(mn), can bedetermined.

In some embodiments, an image sensor is used to detect a compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject. Indetermining the first light intensity in the first wavelength range andthe second light intensity in the second wavelength range, parameters ofthe image sensor are maintained substantially unchanged. For example,parameters affecting the RGB values of an output image of the imagesensor, including aperture, exposure time, focal length, and gain, aremaintained substantially unchanged in the process of determining thefirst light intensity and the second light intensity. Frame rate can beadjusted as long as the frame interval is greater than the exposuretime.

In some embodiments, the memory further stores computer-executableinstructions for controlling the one or more processors to convert eachof the plurality of images of the vessel into three grayscale images,thereby generating the plurality of first grayscale images of the firstwavelength range, the plurality of second grayscale images of the secondwavelength range, and a plurality of third grayscale images of a thirdwavelength range, the first wavelength range, the second wavelengthrange, and the third wavelength range being different from each other;and determining at least two physiological parameters of the subjectbased on the plurality of first grayscale images, the plurality ofsecond grayscale images, and the plurality of third grayscale images.Optionally, the memory further stores computer-executable instructionsfor controlling the one or more processors to determine a first value ofa first color component, a second value of a second color component, anda third value of a third color component for each pixel of a pluralityof pixels of each of the plurality of images; determine a first lightintensity in the first wavelength range, a second light intensity in thesecond wavelength range, and a third light intensity in the thirdwavelength range for each pixel of the plurality of pixels, based on thefirst value, the second value, and the third value; and generate theplurality of first grayscale images of the first wavelength range basedon the first light intensity in each pixel of the plurality of pixels,the plurality of second grayscale images of the second wavelength rangebased on the second light intensity in each pixel of the plurality ofpixels, and the plurality of third grayscale images of the thirdwavelength range based on the third light intensity in each pixel of theplurality of pixels.

In some embodiments, the memory further stores computer-executableinstructions for controlling the one or more processors to determine thefirst light intensity in the first wavelength range, the second lightintensity in the second wavelength range, and the third light intensityin the third wavelength range according to Equation (5):

$\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}} + {Q_{3R}I_{3}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}} + {Q_{3G}I_{3}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}} + {Q_{3B}I_{3}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (5)\end{matrix}$

wherein V_(R) ^(mn) stands for the first value of a first colorcomponent for a pixel (m, n) in a plurality of pixels having m rows andn columns of pixels, V_(G) ^(mn) stands for the second value of a secondcolor component for the pixel (m, n), V_(B) ^(mn) stands for the thirdvalue of a third color component for the pixel (m, n), Q_(1R) stands fora first reference quantum efficiency of the first color component of thepixel (m, n) within the first wavelength range, Q_(1G) stands for asecond reference quantum efficiency of the second color component of thepixel (m, n) within the first wavelength range, Q_(1B) stands for athird reference quantum efficiency of the third color component of thepixel (m, n) within the first wavelength range, Q_(2R) stands for afourth reference quantum efficiency of the first color component of thepixel (m, n) within the second wavelength range, Q_(2G) stands for afifth reference quantum efficiency of the second color component of thepixel (m, n) within the second wavelength range, Q_(2B) stands for asixth reference quantum efficiency of the third color component of thepixel (m, n) within the second wavelength range, Q_(3R) stands for aseventh reference quantum efficiency of the first color component of thepixel (m, n) within the third wavelength range, Q_(3G) stands for aneighth reference quantum efficiency of the second color component of thepixel (m, n) within the third wavelength range, Q_(3B) stands for aninth reference quantum efficiency of the third color component of thepixel (m, n) within the third wavelength range, I₁ ^(mn) stands for thefirst light intensity in the first wavelength range for the pixel (m,n), I₂ ^(mn) stands for the second light intensity in the secondwavelength range for the pixel (m, n), I₃ ^(mn) stands for the thirdlight intensity in the third wavelength range for the pixel (m, n),K_(R) is a constant coefficient for the first color component of thepixel (m, n), K_(G) is a constant coefficient for the first colorcomponent of the pixel (m, n), and K_(B) is a constant coefficient forthe first color component of the pixel (m, n).

As discussed above, Q_(1R), Q_(1G), Q_(1B), Q_(2R), Q_(2G), Q_(2B),Q_(3R), Q_(3G), and Q_(3B) are fixed values, and may be obtained by acalibration test. The three values V_(R) ^(mn), V_(G) ^(mn), and V_(B)^(mn) may be measured by separating the image in each pixel of theplurality of pixels into three different color channels (e.g., a redcolor channel, a green color channel, and a blue color channel).Optionally, V_(R) ^(mn), V_(G) ^(mn), and V_(B) ^(mn) may be representedby grayscale values. Based on Equation (5), the first light intensity inthe first wavelength range for the pixel (m, n), I₁ ^(mn), the secondlight intensity in the second wavelength range for the pixel (m, n), I₂^(mn), and the third light intensity in the third wavelength range forthe pixel (m, n), I₃ ^(mn), can be determined.

In some embodiments, an image sensor is used to detect a compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject. Indetermining the first light intensity in the first wavelength range, thesecond light intensity in the second wavelength range and the thirdlight intensity in the third wavelength range, parameters of the imagesensor are maintained substantially unchanged. For example, parametersaffecting the RGB values of an output image of the image sensor,including aperture, exposure time, focal length, and gain, aremaintained substantially unchanged in the process of determining thefirst light intensity, the second light intensity and the third lightintensity. Frame rate can be adjusted as long as the frame interval isgreater than the exposure time.

In some embodiments, the apparatus is a stand-alone medical monitoringapparatus. In some embodiments, the apparatus for measuring a pluralityof physiological parameters of a subject is integrated into a displayapparatus, e.g., a mobile phone, a laptop, a tablet. In someembodiments, the apparatus for measuring a plurality of physiologicalparameters of a subject is integrated into a health gadget. In someembodiments, the apparatus for measuring a plurality of physiologicalparameters of a subject is integrated into a fitness equipment.

In another aspect, the present disclosure provides a computer-programproduct including a non-transitory tangible computer-readable mediumhaving computer-readable instructions thereon. In some embodiments, thecomputer-readable instructions are executable by a processor to causethe processor to perform converting each of a plurality of images of avessel of a subject provided in response to illumination of the vesselto light of different wavelengths into at least two grayscale images,thereby generating a plurality of first grayscale images of a firstwavelength range and a plurality of second grayscale images of a secondwavelength range, the first wavelength range and the second wavelengthrange being different from each other; and determining one or morephysiological parameters of the subject based on at least the pluralityof first grayscale images and the plurality of second grayscale images.

In some embodiments, the computer-readable instructions are executableby a processor to cause the processor to further perform determining afirst value of a first color component, a second value of a second colorcomponent, and a third value of a third color component for each pixelof a plurality of pixels of each of the plurality of images; determininga first light intensity in the first wavelength range and a second lightintensity in the second wavelength range for each pixel of the pluralityof pixels, based on the first value, the second value, and the thirdvalue; and generating the plurality of first grayscale images of thefirst wavelength range based on the first light intensity in each pixelof the plurality of pixels and the plurality of second grayscale imagesof the second wavelength range based on the second light intensity ineach pixel of the plurality of pixels.

In some embodiments, the computer-readable instructions are executableby a processor to cause the processor to further perform converting eachof the plurality of images of the vessel into three grayscale images,thereby generating the plurality of first grayscale images of the firstwavelength range, the plurality of second grayscale images of the secondwavelength range, and a plurality of third grayscale images of a thirdwavelength range, the first wavelength range, the second wavelengthrange, and the third wavelength range being different from each other;and determining at least two physiological parameters of the subjectbased on the plurality of first grayscale images, the plurality ofsecond grayscale images, and the plurality of third grayscale images.

In some embodiments, the computer-readable instructions are executableby a processor to cause the processor to further perform determining afirst value of a first color component, a second value of a second colorcomponent, and a third value of a third color component for each pixelof a plurality of pixels of each of the plurality of images; determininga first light intensity in the first wavelength range, a second lightintensity in the second wavelength range, and a third light intensity inthe third wavelength range for each pixel of the plurality of pixels,based on the first value, the second value, and the third value; andgenerating the plurality of first grayscale images of the firstwavelength range based on the first light intensity in each pixel of theplurality of pixels, the plurality of second grayscale images of thesecond wavelength range based on the second light intensity in eachpixel of the plurality of pixels, and the plurality of third grayscaleimages of the third wavelength range based on the third light intensityin each pixel of the plurality of pixels.

The foregoing description of the embodiments of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formor to exemplary embodiments disclosed. Accordingly, the foregoingdescription should be regarded as illustrative rather than restrictive.Obviously, many modifications and variations will be apparent topractitioners skilled in this art. The embodiments are chosen anddescribed in order to explain the principles of the invention and itsbest mode practical application, thereby to enable persons skilled inthe art to understand the invention for various embodiments and withvarious modifications as are suited to the particular use orimplementation contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto and their equivalentsin which all terms are meant in their broadest reasonable sense unlessotherwise indicated. Therefore, the term “the invention”, “the presentinvention” or the like does not necessarily limit the claim scope to aspecific embodiment, and the reference to exemplary embodiments of theinvention does not imply a limitation on the invention, and no suchlimitation is to be inferred. The invention is limited only by thespirit and scope of the appended claims. Moreover, these claims mayrefer to use “first”, “second”, etc. following with noun or element.Such terms should be understood as a nomenclature and should not beconstrued as giving the limitation on the number of the elementsmodified by such nomenclature unless specific number has been given. Anyadvantages and benefits described may not apply to all embodiments ofthe invention. It should be appreciated that variations may be made inthe embodiments described by persons skilled in the art withoutdeparting from the scope of the present invention as defined by thefollowing claims. Moreover, no element and component in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element or component is explicitly recited in the followingclaims.

What is claimed is:
 1. A method for determining one or morephysiological parameters of a subject, comprising: providing a pluralityof images of a vessel of the subject in response to illumination of thevessel to light of different wavelengths; converting each of theplurality of images of the vessel into at least two grayscale images,thereby generating a plurality of first grayscale images of a firstwavelength range and a plurality of second grayscale images of a secondwavelength range, the first wavelength range and the second wavelengthrange being different from each other; and determining the one or morephysiological parameters of the subject based on at least the pluralityof first grayscale images and the plurality of second grayscale images;wherein converting each of the plurality of images of the vessel into atleast two grayscale images comprises: determining a first value of afirst color component, a second value of a second color component, and athird value of a third color component for each pixel of a plurality ofpixels of each of the plurality of images; determining a first lightintensity in the first wavelength range and a second light intensity inthe second wavelength range for each pixel of the plurality of pixels,based on the first value, the second value, and the third value; andgenerating the plurality of first grayscale images of the firstwavelength range based on the first light intensity in each pixel of theplurality of pixels and the plurality of second grayscale images of thesecond wavelength range based on the second light intensity in eachpixel of the plurality of pixels.
 2. The method of claim 1, whereindetermining the first light intensity in the first wavelength range andthe second light intensity in the second wavelength range is performedbased on Equation (1): $\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (1)\end{matrix}$ wherein V_(R) ^(mn) stands for the first value of a firstcolor component for a pixel (m, n) in a plurality of pixels having mrows and n columns of pixels, V_(G) ^(mn) stands for the second value ofa second color component for the pixel (m, n), V_(B) ^(mn) stands forthe third value of a third color component for the pixel (m, n), Q_(1R)stands for a first reference quantum efficiency of the first colorcomponent of the pixel (m, n) within the first wavelength range, Q_(1G)stands for a second reference quantum efficiency of the second colorcomponent of the pixel (m, n) within the first wavelength range, Q_(1B)stands for a third reference quantum efficiency of the third colorcomponent of the pixel (m, n) within the first wavelength range, Q_(2R)stands for a fourth reference quantum efficiency of the first colorcomponent of the pixel (m, n) within the second wavelength range, Q_(2G)stands for a fifth reference quantum efficiency of the second colorcomponent of the pixel (m, n) within the second wavelength range, Q_(2B)stands for a sixth reference quantum efficiency of the third colorcomponent of the pixel (m, n) within the second wavelength range, I₁^(mn) stands for the first light intensity in the first wavelength rangefor the pixel (m, n), I₂ ^(mn) stands for the second light intensity inthe second wavelength range for the pixel (m, n), K_(R) is a constantcoefficient for the first color component of the pixel (m, n), K_(G) isa constant coefficient for the first color component of the pixel (m,n), and K_(B) is a constant coefficient for the first color component ofthe pixel (m, n).
 3. The method of claim 1, wherein converting each ofthe plurality of images of the vessel into at least two grayscale imagescomprises converting each of the plurality of images of the vessel intothree grayscale images, thereby generating the plurality of firstgrayscale images of the first wavelength range, the plurality of secondgrayscale images of the second wavelength range, and a plurality ofthird grayscale images of a third wavelength range, the first wavelengthrange, the second wavelength range, and the third wavelength range beingdifferent from each other; and wherein determining the one or morephysiological parameters of the subject based on at least the pluralityof first grayscale images and the plurality of second grayscale imagescomprises determining at least two physiological parameters of thesubject based on the plurality of first grayscale images, the pluralityof second grayscale images, and the plurality of third grayscale images.4. The method of claim 3, wherein converting each of the plurality ofimages of the vessel into three grayscale images comprises: determininga first value of a first color component, a second value of a secondcolor component, and a third value of a third color component for eachpixel of a plurality of pixels of each of the plurality of images;determining a first light intensity in the first wavelength range, asecond light intensity in the second wavelength range, and a third lightintensity in the third wavelength range for each pixel of the pluralityof pixels, based on the first value, the second value, and the thirdvalue; and generating the plurality of first grayscale images of thefirst wavelength range based on the first light intensity in each pixelof the plurality of pixels, the plurality of second grayscale images ofthe second wavelength range based on the second light intensity in eachpixel of the plurality of pixels, and the plurality of third grayscaleimages of the third wavelength range based on the third light intensityin each pixel of the plurality of pixels.
 5. The method of claim 4,wherein determining the first light intensity in the first wavelengthrange, the second light intensity in the second wavelength range, andthe third light intensity in the third wavelength range is performedbased on Equation (2): $\begin{matrix}{\left\{ \begin{matrix}{{{Q_{1R}I_{1}^{mn}} + {Q_{2R}I_{2}^{mn}} + {Q_{3R}I_{3}^{mn}}} = e^{(\frac{V_{R}^{mn}}{K_{R}})}} \\{{{Q_{1G}I_{1}^{mn}} + {Q_{2G}I_{2}^{mn}} + {Q_{3G}I_{3}^{mn}}} = e^{(\frac{V_{G}^{mn}}{K_{G}})}} \\{{{Q_{1B}I_{1}^{mn}} + {Q_{2B}I_{2}^{mn}} + {Q_{3B}I_{3}^{mn}}} = e^{(\frac{V_{B}^{mn}}{K_{B}})}}\end{matrix} \right.;} & (2)\end{matrix}$ wherein V_(R) ^(mn) stands for the first value of a firstcolor component for a pixel (m, n) in a plurality of pixels having mrows and n columns of pixels, V_(G) ^(mn) stands for the second value ofa second color component for the pixel (m, n), V_(B) ^(mn) stands forthe third value of a third color component for the pixel (m, n), Q_(1R)stands for a first reference quantum efficiency of the first colorcomponent of the pixel (m, n) within the first wavelength range, Q_(1G)stands for a second reference quantum efficiency of the second colorcomponent of the pixel (m, n) within the first wavelength range, Q_(1B)stands for a third reference quantum efficiency of the third colorcomponent of the pixel (m, n) within the first wavelength range, Q_(2R)stands for a fourth reference quantum efficiency of the first colorcomponent of the pixel (m, n) within the second wavelength range, Q_(2G)stands for a fifth reference quantum efficiency of the second colorcomponent of the pixel (m, n) within the second wavelength range, Q_(2B)stands for a sixth reference quantum efficiency of the third colorcomponent of the pixel (m, n) within the second wavelength range, Q_(3R)stands for a seventh reference quantum efficiency of the first colorcomponent of the pixel (m, n) within the third wavelength range, Q_(3G)stands for an eighth reference quantum efficiency of the second colorcomponent of the pixel (m, n) within the third wavelength range, Q_(3B)stands for a ninth reference quantum efficiency of the third colorcomponent of the pixel (m, n) within the third wavelength range, I₁^(mn) stands for the first light intensity in the first wavelength rangefor the pixel (m, n), I₂ ^(mn) stands for the second light intensity inthe second wavelength range for the pixel (m, n), I₃ ^(mn) stands forthe third light intensity in the third wavelength range for the pixel(m, n), K_(R) is a constant coefficient for the first color component ofthe pixel (m, n), K_(G) is a constant coefficient for the first colorcomponent of the pixel (m, n), and K_(B) is a constant coefficient forthe first color component of the pixel (m, n).
 6. The method of claim 1,further comprising illuminating the vessel of the subject with acompound light having a first light of the first wavelength range, asecond light of the second wavelength range, a third light of a thirdwavelength range; and detecting light reflected by or transmittedthrough a body part of the subject using an image sensor, therebygenerating the plurality of images of the vessel of the subject.
 7. Themethod of claim 1, further comprising at least one of: (1) illuminatingthe vessel of the subject with a first reference light of the firstwavelength range and determining a first reference quantum efficiency ofthe first color component of a pixel within the first wavelength range,a second reference quantum efficiency of the second color component ofthe pixel within the first wavelength range, and a third referencequantum efficiency of the third color component of the pixel within thefirst wavelength range; (2) illuminating the vessel of the subject witha second reference light of the second wavelength range and determininga fourth reference quantum efficiency of the first color component ofthe pixel within the second wavelength range, a fifth reference quantumefficiency of the second color component of the pixel within the secondwavelength range, and a sixth reference quantum efficiency of the thirdcolor component of the pixel within the second wavelength range; or (3)illuminating the vessel of the subject with a third reference light of athird wavelength range and determining a seventh reference quantumefficiency of the first color component of the pixel within the thirdwavelength range, an eighth reference quantum efficiency of the secondcolor component of the pixel within the third wavelength range, and aninth reference quantum efficiency of the third color component of thepixel within the third wavelength range.
 8. The method of claim 1,wherein the first wavelength range and the second wavelength range arein a wavelength range of near infrared light and visible light.
 9. Themethod of claim 3, wherein the first wavelength range is betweenapproximately 760 nm and approximately 850 nm; the second wavelengthrange is between approximately 850 nm and approximately 960 nm; and thethird wavelength range is between approximately 530 nm and approximately660 nm.
 10. The method of claim 1, wherein the one or more physiologicalparameters of the subject comprise a vein pattern, a pulse wave signal,and a blood oxygen level of the subject.
 11. An apparatus for measuringone or more physiological parameters of a subject using a plurality ofimages of a vessel of the subject provided in response to illuminationof the vessel to light of different wavelengths, comprising: a memory;and one or more processors; wherein the memory and the one or moreprocessors are connected with each other; and the memory storescomputer-executable instructions for controlling the one or moreprocessors to: convert each of the plurality of images of the vesselinto at least two grayscale images, thereby generating a plurality offirst grayscale images of a first wavelength range and a plurality ofsecond grayscale images of a second wavelength range, the firstwavelength range and the second wavelength range being different fromeach other; and determine the one or more physiological parameters ofthe subject based on at least the plurality of first grayscale imagesand the plurality of second grayscale images; wherein the apparatusfurther comprises: a light source configured to illuminate a vessel ofthe subject with a compound light having at least a first light of thefirst wavelength range and a second light of the second wavelengthrange; and an image sensor configured to detecting the compound lightreflected by or transmitted through a body part of the subject, therebygenerating the plurality of images of the vessel of the subject.
 12. Theapparatus of claim 11, wherein the image sensor is a single image sensorcapable of detecting the compound light having the first light of thefirst wavelength range and the second light of the second wavelengthrange.
 13. The apparatus of claim 11, wherein the light source is asingle light source capable of simultaneously emitting the first lightof the first wavelength range and the second light of the secondwavelength range.
 14. The apparatus of claim 11, wherein the memoryfurther stores computer-executable instructions for controlling the oneor more processors to: determine a first value of a first colorcomponent, a second value of a second color component, and a third valueof a third color component for each pixel of a plurality of pixels ofeach of the plurality of images; determine a first light intensity inthe first wavelength range and a second light intensity in the secondwavelength range for each pixel of the plurality of pixels, based on thefirst value, the second value, and the third value; and generate theplurality of first grayscale images of the first wavelength range basedon the first light intensity in each pixel of the plurality of pixelsand the plurality of second grayscale images of the second wavelengthrange based on the second light intensity in each pixel of the pluralityof pixels.
 15. The apparatus of claim 11, wherein the memory storescomputer-executable instructions for controlling the one or moreprocessors to: convert each of the plurality of images of the vesselinto three grayscale images, thereby generating the plurality of firstgrayscale images of the first wavelength range, the plurality of secondgrayscale images of the second wavelength range, and a plurality ofthird grayscale images of a third wavelength range, the first wavelengthrange, the second wavelength range, and the third wavelength range beingdifferent from each other; and determining at least two physiologicalparameters of the subject based on the plurality of first grayscaleimages, the plurality of second grayscale images, and the plurality ofthird grayscale images.
 16. The apparatus of claim 15, wherein thememory further stores computer-executable instructions for controllingthe one or more processors to: determine a first value of a first colorcomponent, a second value of a second color component, and a third valueof a third color component for each pixel of a plurality of pixels ofeach of the plurality of images; determine a first light intensity inthe first wavelength range, a second light intensity in the secondwavelength range, and a third light intensity in the third wavelengthrange for each pixel of the plurality of pixels, based on the firstvalue, the second value, and the third value; and generate the pluralityof first grayscale images of the first wavelength range based on thefirst light intensity in each pixel of the plurality of pixels, theplurality of second grayscale images of the second wavelength rangebased on the second light intensity in each pixel of the plurality ofpixels, and the plurality of third grayscale images of the thirdwavelength range based on the third light intensity in each pixel of theplurality of pixels.
 17. The apparatus of claim 11, wherein the one ormore physiological parameters of the subject comprise a vein pattern, apulse wave signal, and a blood oxygen level of the subject.
 18. Acomputer-program product comprising a non-transitory tangiblecomputer-readable medium having computer-readable instructions thereon,the computer-readable instructions being executable by a processor tocause the processor to perform: converting each of a plurality of imagesof a vessel of a subject provided in response to illumination of thevessel to light of different wavelengths into at least two grayscaleimages, thereby generating a plurality of first grayscale images of afirst wavelength range and a plurality of second grayscale images of asecond wavelength range, the first wavelength range and the secondwavelength range being different from each other; and determining one ormore physiological parameters of the subject based on at least theplurality of first grayscale images and the plurality of secondgrayscale images; wherein converting each of the plurality of images ofthe vessel into at least two grayscale images comprises: determining afirst value of a first color component, a second value of a second colorcomponent, and a third value of a third color component for each pixelof a plurality of pixels of each of the plurality of images; determininga first light intensity in the first wavelength range and a second lightintensity in the second wavelength range for each pixel of the pluralityof pixels, based on the first value, the second value, and the thirdvalue; and generating the plurality of first grayscale images of thefirst wavelength range based on the first light intensity in each pixelof the plurality of pixels and the plurality of second grayscale imagesof the second wavelength range based on the second light intensity ineach pixel of the plurality of pixels.